The present invention is related to radio communication systems and, more particularly, to a system and method for automatically converting unanswered calls to pages in a mobile radio communications system having one or more cells.
Radio communications systems, such as the multi-site trunked land mobile radio system which is described herein as an illustrative example, typically comprise one or more base stations which function as repeaters between mobile radio units. The radio units communicate in a direct call mode or a group call mode. In a direct call, one radio communicates directly with another radio through the repeater base station. In a group call, one radio can communicate with a plurality of radios in a designated group. The radio units transmit on one frequency and receive on a different frequency. The base stations act as a repeater between a sending radio and a receiving radio by receiving signals on the sending radio""s transmit frequency and re-transmitting the signals on the receiving radio""s receive frequency. Such a system is disclosed in U.S. Pat. No. 5,613,201, entitled AUTOMATIC CALL DESTINATION/SYSTEM SELECTION IN A RADIO COMMUNICATION SYSTEM, the disclosure of which is hereby incorporated by reference herein.
The base stations serve a specific geographic area, or cell, and each radio unit is assigned to a specific home cell. The cells may be linked together to cover a large area by linking the base stations so that they can exchange data and transmission signals. This multiple cell arrangement allows two or more radios to communicate even if they are not in communication with the same cell or repeater. The cells monitor each assigned radio by tracking which cell is communicating with the radio. Also, each cell maintains a list of all the radios that are communicating with the base station, regardless of whether the radios are assigned to that cell or not.
When a radio unit initiates a call, the base stations perform call set up functions by determining if the called radio is checked into that cell and then exchanging call set up messages with the called radio. If the called radio is not within the originating cell, then the system determines where the called radio is located and the call information is routed to the called radio""s current cell, which exchanges the call set up messages with the called radio. When a radio is outside the RF coverage area of the cells, or when a radio is turned off, the incoming calls cannot be completed to the called radio. As a result, the called party will not receive the incoming calls.
In the prior art, the caller has only two options when the called radio does not respond to an incoming call. On one hand, the caller can continue to call the destination radio periodically with the expectation that the called unit will eventually either be moved back into the system""s coverage area or be turned on so that it can receive calls. Alternatively, the system may allow the caller to leave a page or message for the called radio. The page will then be delivered when the called radio checks into the system and the called party will be notified of a missed call. The prior art methods of handling missed calls require additional effort by the caller, such as continuing to initiate the call or manually configuring a page message. In the prior art, the caller must select the page function manually and then he or she must set up the page using the radio""s keypad by entering codes, such as the called and calling radio unique identification codes.
It is an object of the present invention to provide a system and method for automatically setting up and configuring a page message when a called radio does not answer an incoming call.
The illustrative system described herein addresses the limitations of the prior art radio communications systems by automatically configuring a page message when a called radio does not respond to an initial call set up message. After determining the called radio""s checked-in cell, the base station for that cell sends an initial message to the radio, such as a xe2x80x9chey youxe2x80x9d message. In response, the called radio transmits a corresponding answer to the base station, such as a xe2x80x9cwhatxe2x80x9d message. However, if the called radio is turned off or outside the coverage area for the cells, then the radio will not receive the initial xe2x80x9chey youxe2x80x9d message and will not respond with the appropriate xe2x80x9cwhatxe2x80x9d message.
When the cell determines that the called radio is not answering, it sends a notification to the calling radio that the called unit is not available. In the present example, the radio communication system automatically configures a page for the called radio. The page will be delivered when the called radio checks back in with one of the cells.
The automatic page set up function may be performed by the calling radio""s cell, the called radio""s home or current cell, or even the calling radio itself Depending upon which device initiates the page, additional information may have to be provided so that the page can be configured properly. For example, if the called radio""s home or current cells configure the page, then they must receive additional information that identifies the calling radio, such as a source identifier.
If the called radio is within the system, then caller identification information may be sent to the called radio as described in co-pending application Ser. No. 09/103,698, entitled CALLER IDENTIFICATION IN A RADIO COMMUNICATION SYSTEM, the disclosure of which is hereby incorporated by reference herein.
It is a feature of the invention to detect when a call in a radio communication system is not answered and to automatically configure a page or message for the called radio to notify the called user that there has been a missed call. The system sends the page to the called radio when the radio checks back into one of the system""s cells.
It is another feature of the present invention to send information that identifies the calling radio so that a page can automatically be configured by the called radio""s home cell or its checked-in cell. The source identification data may be sent along with the initial call set up message from the calling radio. Alternatively, the calling radio may provide the source data after receiving notification that the called party has not answered the call.
It is an additional feature of the invention to provide a system in which the cell serving the calling radio, or the calling radio itself, has the capability to automatically configure the page upon notification that the called radio is not answering the call.
In another embodiment of the present invention, the radio communication system is capable of automatically configuring page messages for individual radios in a calling group when those radios are not in communication with the system during a group call. The group call page message may indicate the calling radio, the group that was called or both. This would allow the called radio user to determine what type of call had been missed.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.